The invention applies more particularly, although not exclusively, to a device for the displacement of a working tool, brought into and held in contact with the convex surface, or alternatively of a support cradle for an employee who has to work on the said surface.
Numerous scaffolding or moveable-cradle systems are already known which can be erected in the vicinity of the surface of a large-dimension part or a similar installation, making it possible to follow the profile of this surface in order to carry out machining, finishing or checking operations thereon. Now these assemblies are generally difficult to construct and install, are relatively expensive and, above all, are poorly suited for following the convex, or even more complex, profile of the part, especially when the latter has large dimensions.
Devices are also known which, starting from a given fixed reference, make it possible to displace a given object or tool in two perpendicular directions. FR-A-2,384,437 thus makes use of a pantograph which can expand in a transverse direction and is carried by a support which is displaceable in a perpendicular direction by means of a control jack. Such an apparatus is more particularly suited to the positioning of a cradle behind an agricultural tractor and, in any case, would as such be unsuited to the construction of an assembly capable of following in regular fashion the profile of a convex surface of large dimensions.
Lastly, devices of a more sophisticated type are known which make it possible to follow the profile of any surface, reproducing at each instant the X and the Y co-ordinates of the successive points of the latter. However, such a device requires that these co-ordinates be memorized and the memorized data retrieved at an appropriate time, which generally results in the use of a complex and expensive electronic piece of equipment.